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Transformerless Phase Controlled DC Supply

IP.com Disclosure Number: IPCOM000074219D
Original Publication Date: 1971-Mar-01
Included in the Prior Art Database: 2005-Feb-23
Document File: 2 page(s) / 38K

Publishing Venue

IBM

Related People

Saia, J: AUTHOR

Abstract

A DC supply can be regulated by means of selective phase control of the firing of a semiconductor controlled rectifier (SCR, or reverse-blocking thyristor). The circuitry includes a start-up circuit, a resetting circuit which normalizes the beginning of each half-cycle and direct coupling of the sense circuit to the output of the supply.

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Transformerless Phase Controlled DC Supply

A DC supply can be regulated by means of selective phase control of the firing of a semiconductor controlled rectifier (SCR, or reverse-blocking thyristor). The circuitry includes a start-up circuit, a resetting circuit which normalizes the beginning of each half-cycle and direct coupling of the sense circuit to the output of the supply.

The start-up phase begins when line voltage is applied from L1, L2 to SCR1, SCR2 and full-wave rectifier D1, D2, D3, D4. At this time E OUT is zero and the SCR's are fired directly on line via D3, D4 and R11 with D1, D2 returning trigger current back to the line. R11 and R22 form a voltage divider chosen so that when the output voltage rises appreciably, D5 conducts and D6 blocks for all subsequent time. At this point, the supply begins the running phase of operation.

In the running mode, zener diode D7 is conducting and the firing angle of the SCR's is controlled by the RT-CT timing network and the interbase voltage on the complementary unijunction Q1. A current path for the interbase current is provided by transistor Q2 which is saturated for all but a few microseconds at zero crossing of line L1-L2. The regulation is accomplished by the direct sensing of E OUT since the interbase voltage of Q1 is equal to E OUT less the breakdown voltage of D7 and saturated Vce of Q2.

Under certain conditions of E OUT range, D7 may be a gas discharge tube, such as a neon lamp.

At the end of every half...